Flexible epoxy anisotropic conductive adhesive film and preparation method thereof

Abstract

The invention discloses a flexible epoxy anisotropic conductive adhesive film and a preparation method thereof, and belongs to the technical field of electronic packaging. The conductive adhesive film is prepared from the following raw material components in parts by mass: 30 to 50 parts of epoxy resin, 15 to 25 parts of curing agent, 0.05 to 0.1 part of silane coupling agent, 3 to 5 parts of hydroxyl-terminated liquid nitrile rubber, 20 to 35 parts of thermoplastic polyurethane, 20 to 30 parts of conductive filler, 1 to 14 parts of solvent-free MXene nanofluid and 1 to 2.5 parts of film forming additive, by introducing a solvent-free inorganic nanofluid modification technology, the stable dispersion and interface compatibility of an MXene reinforced phase in an epoxy resin matrix are improved, and meanwhile, the toughness of the conductive adhesive film is improved, so that the mechanical strength and flexibility of the epoxy anisotropic conductive adhesive film are synergistically improved; the conductive adhesive film prepared by the invention has the advantages of high binding strength, high elongation at break, excellent flexibility and good and stable conductivity, and is suitable for flexible electronic device packaging and dissimilar material interface packaging in a complex environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic packaging materials, and in particular relates to a flexible epoxy-based anisotropic conductive adhesive film and a preparation method thereof, which is suitable for flexible electronic devices and electronic packaging with heterogeneous interface bonding. Background Art

[0002] Anisotropic conductive film (ACF) has excellent conductivity, adhesion, mechanical properties, and strong process adaptability, making it widely used in the electronic packaging industry. With the rapid development of modern electronic technology, the operating environment of electronic equipment and its components is becoming increasingly complex, especially for electronic equipment serving in the field, aviation, ocean, coastal and other fields. The operating environment is even more complex. Epoxy resin, as a key component of conductive adhesive, seriously affects the conductivity, mechanical properties, and thermal properties of conductive adhesive. However, the problems of general-purpose epoxy resin, such as high thermal expansion coefficient, inherent brittleness and easy cracking of conductive adhesive, are becoming increasingly obvious, seriously affecting the structural stability and reliability of packaged devices.

[0003] The Chinese patent application with publication number CN118440619A discloses a flexible conductive adhesive and a method for preparing the same. By adding antimony tin oxide nanoparticles to the conductive adhesive to enhance its mechanical properties, the final measured binding strength is less than 10Mpa. The Chinese patent application with publication number CN110564336A discloses a flexible conductive adhesive and a method for preparing the same. By adding a flexibility modifier to the conductive adhesive to enhance its flexibility, the final elongation at break is 3-5 times that of the unmodified adhesive, with a maximum elongation at break of 42%. However, the overall mechanical properties of the conductive adhesive have not been improved, that is, the toughening effect is poor and the interface compatibility between the reinforcing phase and the matrix is ​​poor, resulting in difficulty in synergistically improving strength and flexibility. Therefore, how to simultaneously improve the binding strength and flexibility of the conductive adhesive remains a major challenge. Summary of the Invention

[0004] In order to overcome the defects in the above-mentioned prior art, the purpose of the present invention is to provide a flexible epoxy-based anisotropic conductive adhesive film and a preparation method thereof. By introducing solvent-free MXene nanofluid modification technology, the good interfacial compatibility between the MXene reinforcement phase and the epoxy resin matrix can be improved, and the MXene reinforcement phase can be stably dispersed in the epoxy resin matrix, while improving its fracture toughness. Therefore, the mechanical strength and flexibility of the epoxy-based anisotropic conductive adhesive film are synergistically improved, solving the technical problems of poor toughening effect and poor interfacial compatibility between the reinforcement phase and the matrix in the existing conductive adhesive film. The flexible epoxy-based anisotropic conductive adhesive film modified by solvent-free MXene nanofluid of the present invention has high binding strength, excellent flexibility, good and stable conductivity and environmental adaptability, which can meet the needs of electronic packaging in complex environments.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A flexible epoxy-based anisotropic conductive adhesive film comprises the following raw materials, calculated by weight: 30-50 parts of epoxy resin, 15-25 parts of curing agent, 0.05-0.1 parts of silane coupling agent, 3-5 parts of hydroxyl-terminated liquid nitrile rubber, 20-35 parts of thermoplastic polyurethane, 20-30 parts of conductive filler, 1-14 parts of solvent-free MXene nanofluid, and 1-2.5 parts of film-forming additive.

[0007] The epoxy resin model is E-51; the curing agent has a latent property of 3-6 months and a curing temperature of above 150° C.; the conductive filler is silica microbeads with an outer layer wrapped in a silver layer, and the film-forming additive is nano-silicon dioxide or nano-aluminum hydroxide.

[0008] The raw materials of the solvent-free MXene nanofluid include the following components by mass: 0.5-2 parts of MAX phase material, 2-10 parts of polyetheramine organic polymer, 0.5-1 part of organosilane, and 12-60 parts of methanol.

[0009] The organic silane is γ-(2,3-epoxypropoxy)propyltrimethoxysilane; and the polyetheramine organic high molecular polymer is polyetheramine M2070.

[0010] A method for preparing a flexible epoxy-based anisotropic conductive adhesive film comprises the following steps:

[0011] Step 1: Disperse epoxy resin, curing agent, silane coupling agent and carboxyl-terminated liquid nitrile rubber in tetrahydrofuran and mix them uniformly with ultrasound to form solution A; dissolve thermoplastic polyurethane in tetrahydrofuran to form solution B; and stir solution A and solution B uniformly to form solution C;

[0012] Step 2: Add solvent-free MXene nanofluid to solution C and stir evenly to obtain solution D; add film-forming additives and conductive fillers to solution D and stir evenly to obtain a colloidal solution;

[0013] Step 3: Cast the colloidal solution onto the release film to form a film, dry it, and then attach it to the PET film for winding and storage to obtain a flexible epoxy-based anisotropic conductive film.

[0014] In step 1, by weight, the epoxy resin: curing agent: silane coupling agent: carboxyl-terminated liquid nitrile rubber: tetrahydrofuran = (30-50): (15-25): (0.05-0.1): (3-5): (30-50); the thermoplastic polyurethane solution: tetrahydrofuran = (20-40): (133-233).

[0015] In step 1, the ultrasonic time is 10-40 min; the stirring conditions for forming solution C are stirring at a temperature of 20-30° C. and a rotation speed of 400-800 rpm for 3-6 h.

[0016] In step 2, the preparation process of the solvent-free MXene nanofluid is as follows: 2-10 parts of polyetheramine organic polymer and 0.5-1 part of organosilane are dissolved in 12-60 parts of methanol solution, and the reaction is carried out under constant temperature condensation reflux for 6-24 hours at a temperature of 30-60°C and a rotation speed of 300-600rpm to obtain a methanol solution of the organic shell layer of the polyetheramine organic polymer; 0.5-2 parts of the cleaned MAX phase are added to the methanol solution of the organic shell layer of the polyetheramine organic polymer and stirred at 25-30°C and argon protection for 6-12 hours, and then rotary evaporation is performed at 40-50°C and 50-100rpm to remove most of the solvent, and then placed in a dialysis bag with a molecular weight cutoff of 3000-5000 and dialyzed for 24-60 hours, changing water 2-8 times in the middle. After dialysis is completed, it is dried at 30-60°C in vacuum for 24-60 hours to obtain a solvent-free MXene nanofluid.

[0017] In step 2, the added amounts of the solvent-free MXene nanofluid, film-forming additive, and conductive filler are 1-14 parts by mass, 1-2.5 parts by mass, and 20-30 parts by mass, respectively.

[0018] In step 2, the stirring conditions for forming solution D are stirring at a temperature of 20-30° C. and a rotation speed of 400-800 rpm for 3-6 hours; the stirring conditions for forming the colloidal solution are stirring at a temperature of 20-30° C. and a rotation speed of 500-800 rpm for 5-10 hours.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. This invention is the first to use solvent-free MXene nanofluid for ACF interface reinforcement, breaking through the technical bottleneck of traditional toughening / reinforcement that cannot be achieved simultaneously; through the special structure of solvent-free MXene nanofluid - "organic shell-inorganic core", the interfacial bonding strength between the MXene reinforcement phase and the epoxy resin is enhanced, solving the technical problem of poor interfacial compatibility between the reinforcement phase and the matrix in existing conductive adhesive films.

[0021] 2. The addition of solvent-free MXene nanofluids in the present invention allows the cross-sectional structure of the prepared epoxy-based anisotropic conductive film to present a uniformly distributed fine concave-convex structure and fibrous stretching marks, significantly improving the toughness and impact resistance of the conductive film, and solving the technical problem of poor toughening effect in existing conductive films; in addition, these nanofluids are also multifunctional, environmentally friendly, thermally stable and widely applicable, making them have important application value in the fields of electronic packaging and flexible electronic devices.

[0022] 3. When the addition amount of solvent-free MXene nanofluid accounts for 10wt% of the total mass of epoxy resin and solvent-free MXene nanofluid, the contact resistance of the conductive adhesive film prepared by the present invention is as low as 8.65, the binding strength reaches 24.10Mpa, and the elongation at break reaches 189.23%, which significantly achieves the synergistic improvement of high binding strength, high flexibility and low resistance. The conductive adhesive film exhibits the best comprehensive performance.

[0023] In summary, the flexible epoxy-based anisotropic conductive adhesive film modified with solvent-free MXene nanofluids in this invention exhibits high binding strength, excellent flexibility, and stable electrical conductivity. Furthermore, it is easy to process and has a long shelf life, allowing for long-term storage at room temperature. Compared to traditional processes, it offers higher production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a fracture cross-sectional view of the bonding cross-section of the epoxy-based anisotropic conductive adhesive film prepared in Example 4.

[0025] Figure 2 Graph showing the test results of the bonding strength of the epoxy-based anisotropic conductive adhesive film of the present invention.

[0026] Figure 3 Graph showing the test results of tensile strength and elongation at break of the epoxy-based anisotropic conductive adhesive film of the present invention. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0028] A flexible epoxy-based anisotropic conductive adhesive film, comprising the following raw materials, calculated by weight: 30-50 parts of epoxy resin; 15-25 parts of curing agent; 0.05-0.1 parts of silane coupling agent; 3-5 parts of hydroxyl-terminated liquid nitrile rubber (CTBN); 20-40 parts of thermoplastic polyurethane; 20-30 parts of conductive filler; 1-14 parts of solvent-free MXene nanofluid; and 1-2.5 parts of film-forming additive. The conductive adhesive film has a thickness of 50-150 μm and comprises a release film layer, a conductive film layer, and a PET film layer stacked in sequence from bottom to top.

[0029] The epoxy resin model is E-51; the curing agent has a latency of 3-6 months and a curing temperature above 150°C. The curing agent model is 180MB and was purchased from Chuzhou Huisheng Electronic Materials Co., Ltd.; the conductive filler is silica microbeads with an outer layer wrapped in a silver layer; and the film-forming additive is nano-silicon dioxide or nano-aluminum hydroxide.

[0030] The raw materials of the solvent-free MXene nanofluid include the following components in parts by mass: 0.5-2 parts of MAX phase material, 2-10 parts of polyetheramine organic polymer, 0.5-1 part of organosilane, and 12-60 parts of methanol; the organosilane is an organosilane having an active group on the side chain group that can be chemically bonded to the terminal amino functional group of the polyetheramine organic polymer, preferably γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560); the polyetheramine organic polymer is a polyetheramine organic polymer containing a terminal amino functional group, preferably polyetheramine M2070.

[0031] A method for preparing a flexible epoxy-based anisotropic conductive adhesive film comprises the following steps:

[0032] Step 1: Disperse 30-50 parts of epoxy resin, 15-25 parts of curing agent, 0.05-0.1 parts of silane coupling agent and 3-5 parts of carboxyl-terminated liquid nitrile rubber (CTBN) in 30-50 parts of tetrahydrofuran by weight, and ultrasonicate for 10-40 minutes to form a uniformly dispersed solution A; dissolve 20-40 parts of thermoplastic polyurethane in 133-233 parts of tetrahydrofuran to form a uniformly dispersed solution B; stir solution A and solution B at a temperature of 20-30° C. and a rotation speed of 400-800 rpm for 3-6 hours to form a uniformly dispersed solution C;

[0033] Step 2: Dissolve 2-10 parts of polyetheramine organic polymer and 0.5-1 part of organosilane in 12-60 parts of methanol solution, and react at a temperature of 30-60°C and a rotation speed of 300-600 rpm for 6-24 hours to obtain a methanol solution of the organic shell layer of the polyetheramine organic polymer; x ) material is added to a methanol solution of an organic shell layer of a polyetheramine organic polymer and stirred at 25-30° C. under argon protection for 6-12 hours; then, after removing most of the solvent by rotary evaporation at 40-50° C. and 50-100 rpm, the material is placed in a dialysis bag with a molecular weight cutoff of 3000-5000 and dialyzed for 24-60 hours, with water changed 2-8 times in the middle. After the dialysis is completed; the material is dried under vacuum at 30-60° C. for 24-60 hours to completely remove the solvent to obtain a solvent-free MXene nanofluid;

[0034] Step 3: Add 1-14 parts of solvent-free MXene nanofluid to solution C, stir at a temperature of 20-30°C and a rotation speed of 400-800 rpm for 3-6 hours to obtain solution D; take 1-2.5 parts of film-forming additive and 20-30 parts of conductive filler and add them to solution D, stir at a temperature of 20-30°C and a rotation speed of 500-800 rpm for 5-10 hours to form a uniform colloidal solution;

[0035] Step 4: Use a casting machine to cast the colloidal solution on the release film and dry it in an oven at 35°C. Then, stick the side of the release film coated with the anisotropic conductive adhesive to the PET film and roll it up for storage to obtain a solvent-free MXene nanofluid-modified flexible epoxy-based anisotropic conductive adhesive film with a thickness of 50-150μm.

[0036] The MXene nanofluids in the following examples were all prepared using the following process: 2 parts of M2070 and 0.5 parts of KH-560 were dissolved in 12 parts of methanol solution, and the mixture was reacted at 30°C and 300 rpm for 6 hours to obtain a KH560-M2070 methanol solution; 1 part of MAX phase was added to deionized water, ultrasonicated for 30 minutes, and added to 5 parts of KH560-M2070 methanol solution, and stirred at 35°C and argon protection for 12 hours; most of the solvent was removed by rotary evaporation at 45°C and 100 rpm, and then dialyzed for 24 hours using a dialysis bag with a molecular weight cutoff of 3500, with the water changed twice in the middle. After the dialysis was completed, the mixture was dried at 30°C in a vacuum for 24 hours to obtain a solvent-free MXene nanofluid.

[0037] Example 1

[0038] A method for preparing a flexible epoxy-based anisotropic conductive adhesive film comprises the following steps:

[0039] 35 parts of epoxy resin, 18 parts of curing agent, 0.07 parts of silane coupling agent and 3.8 parts of CTBN were dispersed in 38 parts of tetrahydrofuran and ultrasonically treated for 18 minutes to form solution A; 28 parts of thermoplastic polyurethane were dissolved in 160 parts of tetrahydrofuran to form solution B; solution A and solution B were stirred at 23°C and 480 rpm for 3.8 hours to form solution C; 1 part of solvent-free MXene nanofluid was added to solution C, and the mixture was stirred at 23°C and 480 rpm for 3.8 hours to obtain solution D; 1.3 parts of gas-phase nano-silicon and 23 parts of conductive filler were added to solution D, and the mixture was stirred at 23°C and 580 rpm for 6.2 hours to obtain a colloidal solution; the colloidal solution was formed into a film on a release film using a casting machine, and the film was attached to a PET film for winding and storage to obtain a flexible epoxy-based anisotropic conductive adhesive film modified with solvent-free MXene nanofluid.

[0040] Example 2

[0041] 42 parts of epoxy resin, 22 parts of curing agent, 0.09 parts of silane coupling agent and 4.6 parts of CTBN were dispersed in 45 parts of tetrahydrofuran and ultrasonically treated for 28 minutes to form solution A; 33 parts of thermoplastic polyurethane were dissolved in 195 parts of tetrahydrofuran to form solution B; solution A and solution B were stirred at 27°C and 650 rpm for 4.7 hours to form solution C; 2.2 parts of solvent-free MXene nanofluid were added to solution C, and the mixture was stirred at 27°C and 650 rpm for 4.7 hours to obtain solution D; 1.7 parts of gas-phase nano-silicon and 27 parts of conductive filler were added to solution D, and the mixture was stirred at 27°C and 720 rpm for 8.3 hours to obtain a colloidal solution; the colloidal solution was formed into a film on a release film using a casting machine, and the film was attached to a PET film for winding and storage to obtain a flexible epoxy-based anisotropic conductive adhesive film modified with solvent-free MXene nanofluid.

[0042] Example 3

[0043] 30 parts of epoxy resin, 15 parts of curing agent, 0.05 parts of silane coupling agent and 3 parts of CTBN were dispersed in 30 parts of tetrahydrofuran and ultrasonically treated for 10 minutes to form solution A; 30 parts of thermoplastic polyurethane were dissolved in 133 parts of tetrahydrofuran to form solution B; solution A and solution B were stirred at 20°C and 400 rpm for 3 hours to form solution C; 2.4 parts of MXene nanofluid were added to solution C, and stirred at 20°C and 400 rpm for 3 hours to obtain solution D; 1 part of gas-phase nano-silicon and 20 parts of conductive filler were added to solution D, and stirred at 20°C and 500 rpm for 5 hours to obtain a colloidal solution; the colloidal solution was formed into a film on a release film using a casting machine, and then laminated to a PET film for winding and storage to obtain a solvent-free MXene nanofluid modified flexible epoxy-based anisotropic conductive adhesive film.

[0044] Example 4

[0045] 30 parts of epoxy resin, 23 parts of curing agent, 0.09 parts of silane coupling agent and 4.8 parts of CTBN were dispersed in 40 parts of tetrahydrofuran and ultrasonically treated for 25 minutes to form solution A; 36 parts of thermoplastic polyurethane were dissolved in 220 parts of tetrahydrofuran to form solution B; solution A and solution B were stirred at 24°C and 600 rpm for 4.5 hours to form solution C; 3.3 parts of solvent-free MXene nanofluid were added to solution C, and the mixture was stirred at 24°C and 600 rpm for 4.5 hours to obtain solution D; 1.6 parts of gas-phase nano-silicon and 28 parts of conductive filler were added to solution D, and the mixture was stirred at 24°C and 650 rpm for 7 hours to obtain a colloidal solution; the colloidal solution was formed into a film on a release film using a casting machine, and the film was attached to a PET film for winding and storage to obtain a flexible epoxy-based anisotropic conductive adhesive film modified with solvent-free MXene nanofluid.

[0046] Example 5

[0047] 50 parts of epoxy resin, 25 parts of curing agent, 0.1 parts of silane coupling agent and 5 parts of CTBN were dispersed in 50 parts of tetrahydrofuran and ultrasonically treated for 40 minutes to form solution A; 40 parts of thermoplastic polyurethane were dissolved in 233 parts of tetrahydrofuran to form solution B; solution A and solution B were stirred at 30°C and 800 rpm for 6 hours to form solution C; 7.1 parts of solvent-free MXene nanofluid were added to solution C, and the mixture was stirred at 30°C and 800 rpm for 6 hours to obtain solution D; 2.5 parts of gas-phase nano-silicon and 30 parts of conductive filler were added to solution D, and the mixture was stirred at 30°C and 800 rpm for 10 hours to obtain a colloidal solution; the colloidal solution was formed into a film on a release film using a casting machine, and the film was attached to a PET film for winding and storage to obtain a flexible epoxy-based anisotropic conductive adhesive film modified with solvent-free MXene nanofluid.

[0048] Example 6

[0049] 35 parts of epoxy resin, 20 parts of curing agent, 0.06 parts of silane coupling agent and 3.5 parts of CTBN were dispersed in 38 parts of tetrahydrofuran and ultrasonically treated for 18 minutes to form solution A; 31 parts of thermoplastic polyurethane were dissolved in 170 parts of tetrahydrofuran to form solution B; solution A and solution B were stirred at 25°C and 500 rpm for 4 hours to form solution C; 6.2 parts of solvent-free MXene nanofluid were added to solution C, and the mixture was stirred at 25°C and 500 rpm for 4 hours to obtain solution D; 1.4 parts of gas-phase nano-silicon and 25 parts of conductive filler were added to solution D, and the mixture was stirred at 25°C and 580 rpm for 6.5 hours to obtain a colloidal solution; the colloidal solution was formed into a film on a release film using a casting machine, and the film was attached to a PET film for winding and storage to obtain a flexible epoxy-based anisotropic conductive adhesive film modified with solvent-free MXene nanofluid.

[0050] Example 7

[0051] 42 parts of epoxy resin, 22 parts of curing agent, 0.08 parts of silane coupling agent and 4.2 parts of CTBN were dispersed in 45 parts of tetrahydrofuran and ultrasonically treated for 28 minutes to form solution A; 33 parts of thermoplastic polyurethane were dissolved in 190 parts of tetrahydrofuran to form solution B; solution A and solution B were stirred at 27°C and 650 rpm for 5 hours to form solution C; 8.9 parts of solvent-free MXene nanofluid were added to solution C, and the mixture was stirred at 27°C and 650 rpm for 5 hours to obtain solution D; 1.9 parts of gas-phase nano-silicon and 27 parts of conductive filler were added to solution D, and the mixture was stirred at 27°C and 700 rpm for 8 hours to obtain a colloidal solution; the colloidal solution was formed into a film on a release film using a casting machine, and the film was attached to a PET film for winding and storage to obtain a flexible epoxy-based anisotropic conductive adhesive film modified with solvent-free MXene nanofluid.

[0052] Example 8

[0053] 48 parts of epoxy resin, 24 parts of curing agent, 0.09 parts of silane coupling agent and 4.7 parts of CTBN were dispersed in 48 parts of tetrahydrofuran and ultrasonically treated for 35 minutes to form solution A; 38 parts of thermoplastic polyurethane were dissolved in 210 parts of tetrahydrofuran to form solution B; solution A and solution B were stirred at 29°C and 750 rpm for 5.5 hours to form solution C; 12 parts of solvent-free MXene nanofluid were added to solution C, and the mixture was stirred at 29°C and 750 rpm for 5.5 hours to obtain solution D; 2.2 parts of gas-phase nano-silicon and 29 parts of conductive filler were added to solution D, and the mixture was stirred at 29°C and 750 rpm for 9 hours to obtain a colloidal solution; the colloidal solution was formed into a film on a release film using a casting machine, and the film was attached to a PET film for winding and storage to obtain a flexible epoxy-based anisotropic conductive adhesive film modified with solvent-free MXene nanofluid.

[0054] Example 9

[0055] 33 parts of epoxy resin, 18 parts of curing agent, 0.07 parts of silane coupling agent and 3.3 parts of CTBN were dispersed in 36 parts of tetrahydrofuran and ultrasonically treated for 20 minutes to form solution A; 29 parts of thermoplastic polyurethane were dissolved in 160 parts of tetrahydrofuran to form solution B; solution A and solution B were stirred at 24°C and 550 rpm for 4 hours to form solution C; 9.6 parts of solvent-free MXene nanofluid were added to solution C, and the mixture was stirred at 24°C and 550 rpm for 4 hours to obtain solution D; 1.5 parts of gas-phase nano-silicon and 24 parts of conductive filler were added to solution D, and the mixture was stirred at 24°C and 620 rpm for 7 hours to obtain a colloidal solution; the colloidal solution was formed into a film on a release film using a casting machine, and the film was attached to a PET film for winding and storage to obtain a flexible epoxy-based anisotropic conductive adhesive film modified with solvent-free MXene nanofluid.

[0056] Example 10

[0057] 40 parts of epoxy resin, 21 parts of curing agent, 0.08 parts of silane coupling agent and 4.5 parts of CTBN were dispersed in 43 parts of tetrahydrofuran and ultrasonically treated for 32 minutes to form solution A; 35 parts of thermoplastic polyurethane were dissolved in 195 parts of tetrahydrofuran to form solution B; solution A and solution B were stirred at 28°C and 700 rpm for 5 hours to form solution C; 13.3 parts of solvent-free MXene nanofluid were added to solution C, and the mixture was stirred at 28°C and 700 rpm for 5 hours to obtain solution D; 2.0 parts of gas-phase nano-silicon and 28 parts of conductive filler were added to solution D, and the mixture was stirred at 28°C and 720 rpm for 8.5 hours to obtain a colloidal solution; the colloidal solution was formed into a film on a release film using a casting machine, and the film was attached to a PET film for winding and storage to obtain a flexible epoxy-based anisotropic conductive adhesive film modified with solvent-free MXene nanofluid.

[0058] Comparative Example 1

[0059] The steps are exactly the same as those in Example 1, except that no solvent-free MXene nanofluid is added.

[0060] The anisotropic conductive films prepared in Examples 1 to 10 and Comparative Example 1 were subjected to performance testing. The films were heat-pressed and cured, and the contact resistance (Z-axis) and insulation resistance (XY-axis) were measured using a multimeter. The bonding strength test was conducted in accordance with the national standard GB7124-86 at room temperature using a microcomputer-controlled universal material testing machine with a fixture movement speed of 20 mm / min. The test results are shown in Table 1.

[0061] Table 1 Various properties of anisotropic conductive adhesive films prepared in Examples and Comparative Examples

[0062]

[0063] From the performance of the flexible epoxy-based anisotropic conductive adhesive film modified with solvent-free MXene nanofluid in Table 1, it can be clearly concluded that when the addition amount of solvent-free MXene nanofluid accounts for 10wt% of the total mass of epoxy resin and solvent-free MXene nanofluid, the material shows the best comprehensive performance balance. This optimized formula not only maintains excellent insulation performance (XY axis, insulation resistance>10 8Ω), while achieving a low contact resistance of 8.65Ω (Z-axis direction), fully meeting the dual requirements of flexible electronic devices for insulation and conductivity. In terms of mechanical properties, the formula exhibits a high binding strength of 24.10MPa and an excellent elongation at break of 189.23%, which is mainly attributed to the unique "organic-inorganic" composite structure of the nanofluid, which effectively enhances the interfacial bonding force and enables the stress to be evenly transmitted. When the addition amount of solvent-free MXene nanofluid accounts for 2.5-15wt% of the total mass of epoxy resin and solvent-free MXene nanofluid, various properties show rapid improvement; and when it exceeds 15wt%, the stress concentration effect caused by the agglomeration of nanoparticles will cause local crack propagation, and the binding strength, tensile strength and elongation at break will be reduced, but it is always higher than that of Comparative Example 1. Combined Figure 1 SEM analysis of the cross-sectional morphology of the conductive film shows that the cross-section of the optimal 10 wt% solvent-free MXene nanofluid sample exhibits uniformly distributed fine concave-convex structures and fibrous stretching marks, demonstrating a typical tough fracture morphology, indicating that the epoxy-based anisotropic conductive film prepared in Example 4 possesses a certain degree of fracture toughness. This invention utilizes the unique "organic shell-inorganic core" structure of the solvent-free MXene nanofluid to enhance interfacial bonding with the epoxy resin. Furthermore, the resulting conductive film exhibits high flexibility, overcoming the contradictions of existing conductive films, which suffer from poor toughening and poor interfacial compatibility between the reinforcing phase and the matrix. This improves stress transfer efficiency and avoids performance degradation caused by localized aggregation.

[0064] In summary, the present invention provides a flexible epoxy-based anisotropic conductive adhesive film and a preparation method thereof. Through the interfacial strengthening effect and stress dispersion ability of solvent-free MXene nanofluid, the difficult problem of the coordinated toughening and reinforcement of traditional conductive adhesives is solved. The film can be widely used in flexible electronic device packaging (such as folding screen circuit connection), interface bonding of dissimilar materials (metal-ceramic substrates), high-reliability military electronic systems and stable interconnection of wearable devices in complex environments, providing an innovative solution for advanced electronic packaging.

Claims

1. A flexible epoxy-based anisotropic conductive adhesive film, characterized in that: The raw materials include the following components by mass: 30-50 parts of epoxy resin, 15-25 parts of curing agent, 0.05-0.1 parts of silane coupling agent, 3-5 parts of hydroxyl-terminated liquid nitrile rubber, 20-35 parts of thermoplastic polyurethane, 20-30 parts of conductive filler, 1-14 parts of solvent-free MXene nanofluid, and 1-2.5 parts of film-forming additive.

2. The flexible epoxy-based anisotropic conductive adhesive film according to claim 1, wherein: The epoxy resin model is E-51; the curing agent has a latent property of 3-6 months and a curing temperature of above 150° C.; the conductive filler is silica microbeads with an outer layer wrapped in a silver layer, and the film-forming additive is nano-silicon dioxide or nano-aluminum hydroxide.

3. The flexible epoxy-based anisotropic conductive adhesive film according to claim 1, wherein: The raw materials of the solvent-free MXene nanofluid include the following components by mass: 0.5-2 parts of MAX phase material, 2-10 parts of polyetheramine organic polymer, 0.5-1 part of organosilane, and 12-60 parts of methanol.

4. The flexible epoxy-based anisotropic conductive adhesive film according to claim 3, wherein: The organic silane is γ-(2,3-epoxypropoxy)propyltrimethoxysilane; and the polyetheramine organic high molecular polymer is polyetheramine M2070.

5. A method for preparing a flexible epoxy-based anisotropic conductive adhesive film, characterized in that: The following steps are involved: Step 1: Disperse epoxy resin, curing agent, silane coupling agent and carboxyl-terminated liquid nitrile rubber in tetrahydrofuran and mix them uniformly with ultrasound to form solution A; dissolve thermoplastic polyurethane in tetrahydrofuran to form solution B; and stir solution A and solution B uniformly to form solution C; Step 2: Add solvent-free MXene nanofluid to solution C and stir evenly to obtain solution D; add film-forming additives and conductive fillers to solution D and stir evenly to obtain a colloidal solution; Step 3: Cast the colloidal solution onto the release film to form a film, dry it, and then attach it to the PET film for winding and storage to obtain a flexible epoxy-based anisotropic conductive film.

6. The method for preparing a flexible epoxy-based anisotropic conductive adhesive film according to claim 5, wherein: In step 1, by weight, the epoxy resin: curing agent: silane coupling agent: carboxyl-terminated liquid nitrile rubber: tetrahydrofuran = (30-50): (15-25): (0.05-0.1): (3-5): (30-50); the thermoplastic polyurethane solution: tetrahydrofuran = (20-40): (133-233).

7. The method for preparing a flexible epoxy-based anisotropic conductive adhesive film according to claim 5, wherein: In step 1, the ultrasonic time is 10-40 min; the stirring conditions for forming solution C are stirring at a temperature of 20-30° C. and a rotation speed of 400-800 rpm for 3-6 h.

8. The method for preparing a flexible epoxy-based anisotropic conductive adhesive film according to claim 5, wherein: In step 2, the preparation process of the solvent-free MXene nanofluid is as follows: 2-10 parts of polyetheramine organic polymer and 0.5-1 part of organosilane are dissolved in 12-60 parts of methanol solution, and the reaction is carried out under constant temperature condensation reflux for 6-24 hours at a temperature of 30-60°C and a rotation speed of 300-600rpm to obtain a methanol solution of the organic shell layer of the polyetheramine organic polymer; 0.5-2 parts of the cleaned MAX phase are added to the methanol solution of the organic shell layer of the polyetheramine organic polymer and stirred at 25-30°C and argon protection for 6-12 hours; then, most of the solvent is removed by rotary evaporation at 40-50°C and 50-100rpm, and then the mixture is placed in a dialysis bag with a molecular weight cutoff of 3000-5000 and dialyzed for 24-60 hours, with water changed 2-8 times in the middle. After dialysis is completed, the mixture is dried at 30-60°C in vacuum for 24-60 hours to obtain a solvent-free MXene nanofluid.

9. The method for preparing a flexible epoxy-based anisotropic conductive adhesive film according to claim 5, wherein: In step 2, the added amounts of the solvent-free MXene nanofluid, film-forming additive, and conductive filler are 1-14 parts by mass, 1-2.5 parts by mass, and 20-30 parts by mass, respectively.

10. The method for preparing a flexible epoxy-based anisotropic conductive adhesive film according to claim 5, wherein: In step 2, the stirring conditions for forming solution D are stirring at a temperature of 20-30° C. and a rotation speed of 400-800 rpm for 3-6 hours; The stirring conditions for forming the colloidal solution are stirring at a temperature of 20-30° C. and a rotation speed of 500-800 rpm for 5-10 hours.

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